Percutaneous microwave ablation of renal parenchymal tumors using a 2.4 GHz gas-cooled probe: initial results and technique

Abstract

Purpose To evaluate the feasibility, safety, and preliminary efficacy of a high-powered, gas-cooled microwave ablation (MWA) system for percutaneous treatment of renal parenchymal tumors. Materials and Methods Over a nine month period, 10 solitary renal parenchymal tumors were treated in 10 consecutive patients (7 male, 3 female, mean age 60) with curative intent using CT-guided MWA with a high-powered, CO2-cooled probe (Neuwave Medical, Madison, WI). A 14G Temno coaxial biopsy system (Cardinal Health, Dublin, OH) was used prior to ablation. The ablation antenna was inserted coaxially using a “single puncture” technique. Immediate post-ablation CT was performed to demonstrate necrosis. Tumor characteristics, procedural details, major and minor adverse events and post-treatment imaging details were recorded. Follow-up imaging was performed with CT or MRI to evaluate for recurrence (defined as persistent tumor enhancement). Serum creatinine levels were obtained pre ablation and 2 weeks post ablation. Results Tumors were classified as exophytic (n=3), parenchymal (n=5), central (n=1), or mixed (n=1). Mean maximum tumor diameter was 2.4 cm ± 0.8 (range: 1.0-3.7). All cases were performed with a single antenna. Mean ablation time (min) was 8 ± 2.6 (range 3.5-10). Mean generator power (W) was 80 ± 24 (range 65-140). Immediate technical success was 100%. There were no major adverse events. One minor complication (10%) included the formation of a renal artery pseudoaneurysm which was successfully treated with embolization. Biopsy results included: grade 2 clear cell renal cell carcinoma (RCC) (n=5), grade 2 papillary RCC (n=2), focal glomerulosclerosis/chronic inflammation (n=2), and non-diagnostic (n=1). Mean time (months) to initial follow-up scan was 2.7 ± 1.3 (range 1-5). Nine of 10 tumors (90%) demonstrated complete necrosis at initial follow up scan. Mean serum creatinine pre and post ablation were 1.3 ± 0.55 and 1.2 ± 0.53, respectively (p=0.76). Conclusion Initial experience with high-powered, gas-cooled percutaneous renal MWA demonstrates high technical and clinical success with preservation of renal function and low complication rates. Further studies are warranted to demonstrate long-term oncologic outcomes.